This invention relates generally to a fluid supply failure protection valve and more particularly to a protection valve which safely accommodates failure of either a hot or a cold water supply to a tempering valve.
Tempered fluid mixing systems are used in a variety of commercial and/or industrial applications, for example, in emergency fixtures such as drench shower stations and/or safety eyewash stations, which are used to rinse hazardous chemicals from a person's skin and clothing or to extinguish burning clothing on a person. A typical system includes a thermostatic mixing valve or tempering valve which automatically blends hot and cold water supply streams to produce a mixed, tempered water output stream having a selected temperature, for example about 27 degrees C. (80 degrees F.).
A known problem with such tempered water mixing systems is that either the hot or cold water supplies may fail. If the cold water supply fails, the mixing valve will supply potentially scalding hot water to the user, causing the risk of burns and further injury. If the hot water supply fails, it is possible to continue using the emergency fixture. However, in this case, only cold water will be supplied to the thermostatic mixing valve, which will cause it to restrict the water flow to a level that is inadequate for proper rinsing or fire extinguishing. Attempts have been made in the prior art to provide for the cut-off of hot water flow in case of a cold water failure, and to provide a bypass flow of cold water should the hot water supply fail. However, these prior art systems require either that the tempering valve be replaced with a tempering valve of an entirely different design, for both tempering the water and accommodating the supply failure, or they require that a separate cold water bypass circuit be plumbed into the system. Accordingly, there is a need for fluid supply failure protection valve which protects a fluid system from failure of both hot and cold water supplies, and which may be integrated into existing systems.